The present invention relates to a vehicle brake control system, and more particularly to a brake system which is employed in combination with a regenerative brake apparatus and which is capable of electronically controlling a braking force of a vehicle according to a brake manipulation force, which comprises a regenerative brake apparatus.
In case that a coordinated brake system is constructed by a regenerative brake apparatus and a friction brake apparatus of a hydraulic or electromotive type which generates a braking force according to the brake manipulation force generated by a driver and a regenerative brake system, it is necessary to electronically control the friction brake apparatus so as to effectively consume a regenerative braking force in view of energy efficiency. During such an electronic control of the coordinated brake system, a demand braking force corresponding to a driver's intent is generated by the friction brake apparatus and the regenerative brake apparatus, and the regenerative braking force is consumed with a priority relative to the braking force generated by the friction brake apparatus.
Japanese Published Patent Application No. 2000-168536 discloses a vehicle brake system which is capable of electronically controlling a braking force. The vehicle brake system comprises a shutoff valve for closing a fluid communication between a master cylinder and wheel cylinders during the electronic brake control, and a hydraulic pressure source constructed by a pump for discharging the working fluid of a reservoir, a motor for driving the pump, and an accumulator for storing the working fluid discharged from the pump. During the electronic control of this brake system, a brake hydraulic pressure in the wheel cylinder is electronically controlled regardless of the master cylinder hydraulic pressure, by using an accumulator inner hydraulic pressure of the hydraulic pressure source through the control of pressure increasing and decreasing valves.